And that is precisely the issue. UA's *A desk maintains that this sort of upgrade can only be done through the *A mechanism (i.e., the dedicated link that one can go to from the Mileaga Plus website), that they see from their end what I see when I try to get an upgrade myself (i.e, a message that the flight is unavailable for upgrades) and that there is no way for me (a passenger) to get to speak to a *A person.
Turkish reservations tell me that the flight is wide open for upgrades (I also see that there are plenty of available seats through any search engine like expedia) and that it is a *A problem that I can't see from my end that the flight is open for upgrades...
According to UA I cannot do this sort of upgrade when I am at the airport checking in, so what do i do?